1. Field of the Invention
The present invention relates to a clutch mechanism that turns on and off transmission of rotative power.
2. Description of Related Art
Conventionally, as a clutch mechanism of this kind, a plate spring hub type clutch mechanism that uses a plate spring for turning on and off of transmission of rotational driving force from a rotor, which is a driving side rotating body, to an armature, which is a driven side rotating body, is known (e.g., JP-A-2003-247565 corresponding to U.S.2003/0159901A1).
In the plate spring hub type clutch mechanism, upon energization of an electromagnet, the armature is attracted and coupled to the rotor-side, so that the rotational driving force is transmitted, and when the energization of the electromagnet is stopped, the armature is detached from the rotor by resilient force (repulsive force) of the plate spring, so that the transmission of rotational driving force is interrupted.
More specifically, the armature and an inner hub are joined together via the plate spring, and the armature is displaced in a direction away from the rotor by the resilient force of the plate spring.
Because of growing needs of low NV (vibration noise) and low cost in recent years, reduction of an operating noise of the plate spring hub type clutch mechanism having a simple configuration offers highly promising prospects.
In the conventional technology of JP-A-2003-247565, for example, a rubber member is disposed between the inner hub and the plate spring. By mitigating an impact when the armature is attracted to the rotor side and the armature thereby collides with the rotor by the rubber member, the operating noise is reduced.
On the other hand, conventionally, a rubber hub type clutch mechanism is also known (e.g., JP-UM-A-62-167936). The rubber hub type clutch mechanism obtains the repulsive force for detaching the armature from the rotor by the rubber member instead of the plate spring.
In the conventional technology of JP-UM-A-62-167936, a hub plate is joined to the armature, and the hub plate and the inner hub are joined together via an annular rubber member. By resilient force (repulsive force) of the rubber member, the armature and the hub plate are displaced in a direction away from the rotor.
In JP-UM-A-62-167936, it is described that the operating noise is reduced as a result of a projection portion formed on the outer diameter side of the rubber member integrally with the rubber member being placed between the hub plate and the armature.
As a result of in-depth consideration of the present inventors, it has turned out that the operating noise when the armature is attracted to the rotor is further reduced by limiting vibration of the armature immediately after the collision with the rotor.
However, in the above conventional technology of JP-A-2003-247565, the impact at the time of collision between the armature and the rotor is only mitigated, and vibration of the armature immediately after the collision cannot be limited. Therefore, reduction of the operating noise is insufficient.
On the other hand, the above conventional technology of JP-UM-A-62-167936 relates to the rubber hub type clutch mechanism. The rubber hub type clutch mechanism has different basic configuration from the plate spring hub type clutch mechanism. Thus, the configuration of the above conventional technology of JP-UM-A-62-167936 cannot be simply applied to the plate spring hub type clutch mechanism.